It's the end of the month, and I don't have much in the house, but I'm using what I do have:
Bones from pork loin chops and pork rib chops.
Carrot peels, celery ends, garlic hulls
A bit of leftover squash.
Since I have some green things in there, I'm going to keep this on a really low and gentle bubble, and add them in half-way through to avoid smelly chemical reactions when the chlorophyll is released.